This invention relates to a method of supporting communication between a first network node and a second network node of a communications network, wherein information is exchanged about label resources between the second network node and one or more further network nodes of the communications network using a label distribution protocol, whereby the establishment of shortcuts, each of which is formed by a direct Layer 2 connection assigned to a Layer 3 forwarding relationship, is made possible between the second network node and the further network nodes. The invention is further directed to a communications network comprising these network nodes, with the second network node and the one or more further network nodes comprising switch controllers which are designed to exchange information about label resources using a label distribution protocol. The invention is further directed to the network nodes and switch controllers used in such a method and network.
The invention is based on a new forwarding concept for integrating, for example, IP (=Internet Protocol) and ATM (=Asynchronous Transfer Mode), the multiprotocol label switching (MPLS) concept. This concept combines the Layer 2 functionalityxe2x80x94e.g., ATM switchingxe2x80x94and the Layer 3 functionalityxe2x80x94e.g., IP routing. Network nodes which follow this concept are referred to as xe2x80x9cintegrated switch routersxe2x80x9d. They are composed of a Layer 3 router, a switch controller, and a Layer 2 switch.
One pre-MPLS technology for implementing multiprotocol label switching is the Ipsilon flow switching concept. Forwarding decisions in Layer 3 are made only for the first data packets of a flow. Then, the associated Layer 3 forwarding relationship is assigned a shortcut, which is formed by a direct Layer 2 connection. The establishment of such shortcuts is based on the fact that information about available label resources and about the assignment of labels to shortcuts is exchanged between the network nodes of the multiprotocol label switching domain. The label resources are thus managed jointly by the network nodes of the multiprotocol label switching domain, and the establishment of shortcuts is thus coordinated. Without the exchange of this information, the establishment of a shortcut is not possible. The advantage of this concept is that after establishment of a shortcut, no Layer 3 forwarding decisions need be made in the multiprotocol label switching domain, whereby the user data communication can be considerably accelerated.
The invention has for its object to further accelerate the user data communication in a mixed network environment with LDP-capable network nodes and non-LDP-capable network nodes.
This object is attained by a method of supporting communication between a first network node and a second network node of a communications network, the method comprising exchanging information about label resources between the second network node and one or more further network nodes of the communications network using a label distribution protocol, whereby the establishment of shortcuts, each of which is formed by a direct Layer 2 connection assigned to a Layer 3 forwarding relationship, is made possible between the second network node and the further network nodes, wherein the first network node, instead of exchanging information about label resources with the second network node using a label distribution protocol, is preconfigured with a set of label resources, that the second network node manages the assignment of the label resources available for a connection between the first network node and the second network node and preconfigured in the first network node, and that the second network node assigns to a shortcut one of the labels of the preconfigured set of label resources which are available for the connection with the first network node, thereby extending the shortcut through the second network node to the first network node.
The invention further resides in a network, network nodes and switch controllers for implementing this method, all as described in more detail below.
The idea underlaying the invention is to extend a shortcut from an LDP-capable network node of an MPLS domain towards a non-LDP-capable network node which does not exchange information about label resources with the network nodes of this MPLS domain. To make this possible, the non-LDP-capable network node is preconfigured with a set of label resources. The LDP-capable network node connected to the non-LDP-capable network node manages the labels available for the connection between these network nodes, and assigns these labels to shortcuts without interacting with the non-LDP-capable network node.
One advantage of the invention is that this allows a user data stream to be forwarded via a shortcut up to the host, so that user data communication is accelerated and the calculating capacity necessary therefor is reduced.
Another advantage of the invention is that in spite of that advantage being gained, the non-LDP-capable network node can be considerably simpler in construction than an LDP-capable network node, because it need not process a label distribution protocol, for example. This makes the use of this solution in access nodes particularly attractive. As no internal communication takes place between the LDP-capable network node and the non-LDP-capable network node, the bandwidth available for user data communication between these network nodes is greater than with two comparable LDP-capable network nodes.
A further advantage of the invention is that it can be incorporated into existing communications systems at low cost.
Further advantageous features of the invention are defined in the subclaims.